1. Field of Invention
The present invention relates to an electrooptical apparatus such as an active matrix liquid crystal apparatus driven by thin-film transistors (hereinafter also referred to as TFTs), and also to a method of producing such an electrooptical apparatus. More particularly, the present invention relates to an electrooptical apparatus such as a liquid crystal apparatus suitable for use in a liquid crystal projector, and including peripheral circuits such as a data line driving circuit and a scanning line driving circuit, wherein a light blocking film is disposed under each TFT. The present invention further relates to a method of producing such an electrooptical apparatus.
2. Description of Related Art
In conventional liquid crystal apparatus having built-in peripheral circuits, peripheral circuits such as a data line driving circuit, a scanning line driving circuit, and a sampling circuit are formed on a TFT array substrate, which is one of two substrates between which a liquid crystal is disposed. In general, these peripheral circuits are produced using the same production process as that for producing TFTs for switching an image signal applied to pixel electrodes provided in respective pixels (hereinafter such TFTs will also be referred to as pixel TFTs) so as to achieve a high production efficiency.
On the TFT array substrate, there are provided a great number of data lines and scanning lines in an image displaying area in contact with the liquid crystal, wherein these data lines and scanning lines cross each other at different layer levels. Input/output interconnections connected to peripheral circuits are disposed in a sealing area, outside the image displaying area and in contact with a sealing material for enclosing a liquid crystal, and in a peripheral area outside the sealing area. More specifically, leading interconnections which extend from the data lines, the scanning lines, and the capacitance lines, and which serve as the input/output interconnections for the peripheral circuits, are disposed in the sealing area and image signal lines, control signal lines, power supply lines, clock signal lines, and other signal lines, connected to external input terminals, and are disposed in the peripheral area.
In particular, in a liquid crystal apparatus having a sampling circuit as a peripheral circuit, when an image signal is supplied to an image signal line via an external input terminal, the image signal is sampled, from one data line to another, by sampling switches of the sampling circuit, in response to a sampling circuit driving signal output with predetermined timing from the data line driving circuit.
Because the image signal line is a signal line used to supply the image signal itself, which defines the voltage applied to the liquid crystal, it is extremely important that the image signal line has a low electric resistance and a small time constant to prevent degradation in the picture quality. To this end, the image signal line is generally formed of a thin metal film such as an aluminum film which has the lowest resistivity of all thin films used in the active matrix TFT liquid crystal apparatus, and which is also used to form data lines.
On the other hand, there are no currently available techniques which can be used to form the scanning lines of a thin metal film or a thin metal silicide film, because existing techniques would be subject to the problem that the scanning lines would peel off during a high-temperature process performed after the formation of the scanning lines. For the above reason, the scanning lines are generally formed of a thin polysilicon film. The interconnection formed of a thin polysilicon film has as high a resistance as 200 times that of an interconnection formed of a thin metal film, and thus has a correspondingly high time constant. For the above reason, if the image signal line was formed of a thin polysilicon film, degradation in the image quality would occur depending on the resistance and the time constant of the interconnection employed as the image signal line. In practice, to avoid the above problem, the image signal line is formed of a thin metal film, as described above.
In the above-described type liquid crystal apparatus including the peripheral circuit, if there is only one image signal line, it is possible to form the image signal line with an interconnection formed of a thin metal film at the same single layer level (produced in the same process) over the entire path from an external input terminal disposed at an end of a substrate to respective sampling switches of the sampling circuit. However, in the case where a plurality of image signal lines are required to transmit image signals expanded into a plurality of phases so as to handle high-frequency driving operation in the liquid crystal apparatus, or in the case where a plurality of image signal lines are required to handle respective colors of an RGB color image signal, at least one image signal line has to cross another image signal line somewhere in the path to sampling switches. That is, it is impossible to produce interconnections for all image signal lines using only a thin metal film at the same layer level.
Therefore, a relay interconnection is formed using a polysilicon film at a different layer level separated by an interlayer insulating film from the thin metal film. More specifically, one interconnection includes a first interconnection (main interconnection) made of a thin metal film and disposed at a crossing point. Another interconnection includes a second interconnection (relay interconnection) made of a thin polysilicon film extending at a different level and crossing below or above the first interconnection via an interlayer insulating film, wherein the second interconnection is electrically connected to a part of the interconnection made of a thin metal film via contact holes formed, at both sides of the crossing point, in the interlayer insulating film.
If only a part, which crosses another interconnection, is constructed in the form of a relay interconnection made of a thin polysilicon film, and the other parts are constructed in the form of main interconnections made of a thin metal film which are connected to each other via the relay interconnection as described above, then the relay interconnection made of the thin polysilicon film has a very small length, and thus the existence of the relay line made of the thin polysilicon film does not cause the image signal line to have so significant increases in the overall resistance and time constant that can cause a problem to occur during practical applications.
When a liquid crystal apparatus of the above-described type is used as a light valve in a liquid crystal projector or the like, a projection light ray is generally incident on an opposite substrate opposing, via a liquid crystal layer, a TFT array substrate. If the channel region made of an a-Si (amorphous silicon) film or a p-Si (polysilicon) film of TFTs is exposed to the projection light, a photocurrent is generated in the channel region by the photoelectric conversion effect, and the transistor characteristic of the TFTs are degraded. To avoid the above problem, a light blocking film, called a black matrix or a black mask, made of a metal material such as Cr (chromium), or a black resin is formed on the opposite substrate so that each TFT is covered with the light blocking film. This light blocking film defines opening areas (through which the projection light ray is allowed to pass) of the respective pixels. That is, the light blocking film serves not only to prevent the p-Si layer of TFTs from being exposed to light, but also to improve the contrast and prevent colors from mixing.
In the case of the liquid crystal apparatus for use as a light valve, in particular when a normal stagger type or coplanar type a-Si or p-Si TFT with the top gate structure (in which the gate electrode is disposed above the channel on the TFT array substrate) is employed, it is required to prevent the channels of TFTs from being exposed to a part of projection light reflected from a projection optical system of the liquid crystal projector and striking the TFT array substrate. Furthermore, it is also required to prevent the channels of TFTs from being exposed to a part of light reflected from the surface of the TFT array substrate which can occur when the projection light passes through the light valve. Still furthermore, when a plurality of liquid crystal apparatus are combined to handle a colored image, it is required to prevent the channel of TFTs from being struck by a leakage light component emerging from another liquid crystal apparatus and incident from the TFT array substrate side. In some known techniques, to avoid the above problem, as disclosed for example in Japanese Unexamined Patent Publication No. 9-127497, Japanese Patent Publication No. 3-52611, Japanese Unexamined Patent Publication No. 3-125123, and Japanese Unexamined Patent Publication No. 8-171101, an additional light blocking film made of transparent refractory metal or the like is provided on a TFT array substrate, at locations opposite to TFTs (that is, at locations under the TFTs).
Problems to be Solved by the Invention.
To meet the general requirement for improved image quality, the driving frequency of liquid crystal apparatus of XGA, SXGA, or EWS type becomes increasingly higher. With the increase in the driving frequency, the number of expanded phases becomes large. More specifically, 24 phases are employed recently.
However, to handle such a large number of expanded phases, it is required that a correspondingly great number of image signal lines be disposed in parallel. As a result, the relay interconnections made of the thin polysilicon film become longer. Because the resistance of the interconnection increases in proportion to the length of the interconnection, the resistance of the relay interconnections becomes large. As a result, the image signal lines have a large resistance and a large time constant which result in degradation in the image quality. More specifically, an increase in the resistance or the time constant of image signal lines causes the image signal to have fluctuations via coupling capacitance or causes the image signal on the previous line (column) to be written onto the next line (column), and thus a ghost or crosstalk occurs.
To avoid the above problem, if the relay interconnections in the sealing area or periphery area are formed of a thin metal film which is not used in the pixel area, the efficiency of the production process based on the planar technology becomes low. As a result, the production cost becomes high and the fundamental advantages of the liquid crystal apparatus of the type including built-in peripheral circuits are lost.
In view of the above, it is an object of the present invention to provide an electrooptical apparatus, such as a liquid crystal apparatus of the type including a built-in peripheral circuit, in which the resistance of input/output interconnections in the peripheral circuit is reduced by effectively using thin films forming pixels, thereby making it possible to display a high-quality image.
Means for Solving the Problems.
According to a first aspect of the present invention, to solve the above problems, there is provided an electrooptical apparatus including an electrooptical material disposed between a pair of substrates wherein, on one of the substrates, there are provided: a plurality of pixel electrodes arranged in a matrix fashion; a plurality of thin-film transistors that drive the plurality of pixel electrodes, respectively; a plurality of data lines connected to the plurality of thin-film transistors, respectively, and a plurality of scanning lines connected to the plurality of thin-film transistors, the plurality of data lines and the plurality of scanning lines crossing each other at different layer levels, an electrically-conductive light blocking film disposed such that at least a channel region of each of the plurality of thin-film transistors is covered with the light blocking film when viewed from the side of the one of substrates; at least a peripheral circuit for supplying an image signal to the data lines; and peripheral interconnections that input and output predetermined types of signals including the image signal to and from the peripheral circuit; wherein the peripheral interconnections include: an interconnection made of a first conductive film, which is one of a plurality of thin-film layers constituting the thin-film transistors, the data lines, and the scanning lines; and an interconnection made of the light blocking film.
In the electrooptical apparatus according to the first aspect of the invention, there are provided peripheral circuits such as a sampling circuit and a data line driving circuit on one of substrates, so that the electrooptical apparatus acts as the type including built-in peripheral circuits. The electrically-conductive light blocking film is disposed such that at least the channel region of each of the plurality of thin-film transistors is covered with the light blocking film when viewed from the side of the one of substrates. Therefore, the channel region of each thin-film transistor is prevented by the light blocking film from being exposed to light, such as a reflected light ray coming from the side of the one of substrates, thereby preventing the thin-film transistors from being degraded in characteristics by the reflected light. In particular, in the present invention, the peripheral interconnections include an interconnection made of a first conductive film (for example the thin metal film forming the data lines) which is one of a plurality of thin-film layers constituting the thin-film transistors, the data lines, and the scanning lines, and also include an interconnection made of the light blocking film.
It is possible to obtain a lower resistance for the peripheral interconnections by employing the light blocking film with good electrical conductivity as the material for the peripheral interconnections, compared with the conventional peripheral interconnections made of one conductive thin film (hereinafter referred to as a second conductive film) selected from the plurality of thin films forming the thin film transistors, data lines, and scanning lines except the first conducive film, wherein the second conductive film is worse in conductivity than the first conductive film, and the light blocking film is better in conductivity than the second conductive film. For example, when a polysilicon film is used as the second conductive film, if the light blocking film is made of an electrically-conductive and refractory metal film including Ti (titanium), Cr (chromium), W (tungsten), Ta (tantalum), Mo (molybdenum), or Pd (lead), then the interconnection resistance of the peripheral interconnection is greatly reduced. In this technique, the light blocking film serves not only as a film for preventing the thin-film transistors from being exposed to light, but also as a peripheral interconnection, and thus the structure and the production process can be simplified.
Therefore, various signals, including an image signal, can be input and output to and from the peripheral circuits via the peripheral interconnections that have low resistance. Therefore, the driving frequency of the electrooptical apparatus can be increased or the number of expanded phases or the number of image signals which are input in parallel can be increased without causing voltage fluctuations, ghosts, or crosstalk due to capacitive coupling associated with the peripheral interconnections such as image signal lines, which are problems in the conventional technique, thereby ensuring that a high-quality image is displayed.
In one mode of the electrooptical apparatus according to the first aspect of the invention, the peripheral interconnections include a single-layer interconnection made of the first conductive film in the form of a single layer when viewed in the thickness direction of the one of substrates; and a two-layer interconnection constructed in the form of two layers when viewed in the thickness direction of the one of substrates, one of the two layers being made of a second conductive film, which is one of the plurality of thin-film layers constituting the data lines and the scanning lines, the other layer being made of the light blocking film.
In this mode, the single-layer interconnection of the peripheral interconnection is made of the first conductive film into a single layer structure when viewed in the thickness direction of the one of substrates. The two-layer interconnection of the peripheral interconnection is made of the second conductive film and the light blocking film into a two layer structure when viewed in the thickness direction of the one of substrates. Therefore, when the first conductive film is made of a thin film layer having a low resistance such as a metal film, and the second conductive film is made of a thin film layer such as a polysilicon film having a higher resistance than the first conductive film, the overall resistance of the peripheral interconnection becomes lower by an amount corresponding to the reduction in the resistance of the two-layer interconnection achieved by the existence of the light blocking film compared with a combination of two types of conventional peripheral interconnections made of the first and second conductive films, respectively, into a single layer structure, which cross each other somewhere. For example, when the second conductive film is formed of a polysilicon film and the light blocking film is formed of a refractory metal film having a high conductivity including Ti, Cr, W, Ta, Mo, or Pd, the resistance of the two-layer interconnection, measured along the interconnection, is dominated by the sheet resistance of the light blocking film. Thus, it becomes possible to greatly reduce the resistance of the two-layer interconnection compared with the single-layer interconnection formed of only a single layer of polysilicon according to the conventional technique. Furthermore, in the present invention, the resistance of the single-layer interconnection can be reduced by employing the first conductive film such as Al (aluminum). Thus, the peripheral interconnection including a single-layer interconnection and a two-layer interconnection electrically connected in series to each other has a low enough resistance.
Furthermore, the peripheral interconnection has a redundant structure in which even if either a part formed of the thin polysilicon film or a part formed of the light blocking film of the two-layer interconnection is broken due a foreign particle or the like, the electrical conduction is still maintained via the remaining part. Since the two-layer interconnection that has the small resistance is formed using the first conductive film, which is also used to form pixels, and also using the light blocking film which is also used to protect the TFTs from light, the two-layer interconnection according to the present invention can be produced without causing a significant reduction in the production efficiency of the production process of the electrooptical apparatus with a planar structure. Thus, it is possible to achieve fundamental advantages of the electrooptical apparatus of the type including built-in peripheral circuits.
In the peripheral interconnection including the single-layer interconnection and the two-layer interconnection according to the present invention, the single-layer interconnection made of the same film as the first conductive film may also be formed into a two-layer or three-layer structure by adding a redundant interconnection. Such a multilayer interconnection still includes a single-layer interconnection according to the invention. Furthermore, an additional redundant interconnection may be added to the two-layer interconnection made of the same film as the second conductive film and the light blocking film so as to obtain an interconnection structure including three or more layers. Such a multilayer interconnection still includes a two-layer interconnection according to the invention.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnection includes the two-layer interconnection, the second conductive film may have a resistance higher than that of the first conductive film.
In this structure, the first conductive film, such as aluminum, has the lowest resistance of all thin films used to form the thin-film transistors, and the second conductive film, such as the low-resistance polysilicon film, has the next lowest resistance of all thin films used to form the thin-film transistors. As a result, the overall resistance of the peripheral interconnection becomes lower by an amount of reduction in the resistance of the two-layer interconnection achieved by employing the light blocking film having a high conductivity compared with the case where peripheral interconnections are formed of first and second conductive films in a single-layer structure crossing each other at different layer levels, according to the conventional technique.
In a mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the two-layer interconnection, the electrooptical apparatus further includes a first interlayer insulating film disposed between the light blocking film and the thin-film transistors; and a second interlayer insulating film disposed between the first conductive film and the second conductive film; wherein the two-layer interconnection includes a relay interconnection which is electrically connected to a part of the single-layer interconnection and which crosses another part of the single-layer interconnection in a three-dimensional fashion via the first or second interlayer insulating films.
In this mode, the relay interconnection is electrically connected to a part of the single-layer interconnection and crosses another part of the single-layer interconnection in a three-dimensional fashion via the first or second interlayer insulating film (that is, the relay interconnection passes over or under another part of the single-layer interconnection). That is, because peripheral interconnections must cross each other somewhere, it is impossible to dispose all peripheral interconnections at the same layer level. This problem is solved by employing a relay interconnection. That is, the relay interconnection makes it possible to dispose peripheral interconnections into any desired pattern.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the two-layer interconnection includes the relay interconnection, the peripheral interconnections may include an image signal line for supplying the image signal from an external input terminal; and the peripheral circuit may include a sampling circuit for sampling the image signal, a data line driving circuit for driving the sampling circuit with predetermined timing thereby supplying the image signal on the image signal line to the plurality of data lines via the sampling circuit, and a scanning line driving circuit for driving the scanning lines.
This allows the image signal line, which has to cross another peripheral interconnection somewhere and which could not be disposed in a desired manner if it were disposed at the same layer level, to be disposed in any desired pattern via a relay interconnection.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the image signal line, the image signal may be expanded to N phases (where N is an integer equal to or greater than 2) and there may be provided N image signal lines, and the N image signal lines may include a relay interconnection at a location where some of the N image signal lines cross to each other.
In this structure, increases in the resistance and time constant of the relay interconnection are minimized even when long relay interconnections are required to handle a large number (N) of expanded phases, or to handle a large number of image signals which are input in parallel as is the case with RGB color image signals, in particular compared with the case where relay interconnections are formed of a single layer of a thin polysilicon film according to the conventional technique.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the image signal line, the electrooptical apparatus may further include a plurality of sampling circuit driving signal lines that supply a sampling circuit driving signal from the data line driving circuit to the sampling circuit, and at least a part of the sampling circuit driving signal lines which crosses any of the image signal lines may be made of the relay interconnection.
This technique makes it possible to form sampling circuit driving signal lines extending from the data line driving circuit to the sampling circuit using relay interconnections disposed at locations where they cross for example an image signal line. Furthermore, this technique allows the interconnection layout to be designed in a more flexible manner. Still furthermore, increases in the resistance and time constant of the sampling circuit driving signal lines can be reduced compared with the case where relay interconnections of the sampling circuit driving signal lines are formed of a single layer of a thin polysilicon film according to the conventional technique.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the two-layer interconnection, the second conductive film and the light blocking film both constituting the two-layer interconnection may be electrically connected to each other via a contact hole formed in the first interlayer insulating film.
This technique makes it possible to obtain a high-reliability two-layer interconnection whose layers are electrically connected to each other via a contact hole. The contact hole for this purpose may be formed relatively easily using the process for producing the pixel TFTs.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the two-layer interconnection, the first conductive film may be made of a thin metal film forming the data lines connected to the source or drain of the thin-film transistors, and the second conductive film may be made of a thin polysilicon film forming the scanning lines including gate electrodes of the thin-film transistors.
In this case, because the single-layer interconnection is formed of the thin metal film, such as aluminum, the single-layer interconnection has a low resistance. Although the part formed of the thin polysilicon film has a resistance 200 times greater than that of the thin metal film, that part has a parallel path formed of the light blocking film with electrical conductivity, and thus the overall resistance of the two-layer interconnection is much smaller than the resistance of the thin polysilicon film. If the electrically-conductive light blocking film is made of metal, including at least one of Ti, Cr, W, Ta, Mo, or Pd or a metal silicide, the overall resistance and time constant can be reduced to several tenths (for example, about xc2xd or ⅓) of those that would be obtained with a single-layer of thin polysilicon film.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the two-layer interconnection, the electrooptical apparatus may further include a sealing material for enclosing the electrooptical material between the pair of substrates, and at least three films including the first conducive film, the second conductive film, and the light blocking film may be disposed in a multilayer fashion in a sealing area, in contact with the sealing material, on the one of substrate, around the periphery of the electrooptical material, and furthermore, the leading interconnections of the data lines and scanning lines extending across the sealing area may be formed of at least one of the above-described three films.
In this structure, the electrooptical material is enclosed by the sealing material between the pair of substrates such that a so-called electrooptical cell is formed. Because at least three films including the first conducive film, the second conductive film, and the light blocking film are disposed in a multilayer fashion in the sealing area around the periphery of the electrooptical material, it is possible to minimize the variation in the gap, including the effects of various thin films, between the two substrates over the entire sealing area around the electrooptical material. Thus, it becomes possible to more precisely control the gap of the liquid crystal cell when the gap is controlled by the sealing material containing gap materials with a particular diameter. Furthermore, by using the leading interconnections of the data lines and scanning lines, which are formed of at least one of the three films and which extend across the sealing area, it is possible to supply signals into the image displaying area without encountering any problems.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the three-layer film is disposed in the sealing area, the leading interconnections may each include a two-layer or three-layer interconnection whose layers are made of at least two of the three films, respectively, wherein the layers are electrically connected to each other via a contact hole. This structure allows a reduction in the resistance of the leading interconnections.
Alternatively, the leading interconnections may each include a single-layer interconnection made of one of the three films, and the other two films of the three films may be dummy interconnections which do not serve as an interconnection in the sealing region. In this structure, the gap in the sealing area between the two substrates is determined by the thickness of the dummy interconnections, and thus it is possible to relatively easily minimize the variation in the gap.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the peripheral interconnections include the two-layer interconnection, the two-layer interconnection may have such a structure that the part made of the light shielding film is covered with the part made of the second conductive film when viewed from the side of the other one of the pair of substrates.
In this mode, because the part, made of the light blocking film, of the two-layer interconnection is covered with the part made of the second conductive film, the single-layer interconnection such as an image signal line crossing the part made of the light blocking film has a less capacitive coupling with the part made of the light blocking film, and thus the increase in the time constant associated with the single-layer interconnection causes by the capacitive coupling can be suppressed. In particular, when the second conductive layer is disposed between the first conductive film and the light blocking film, it is possible to suppress the increase in the capacitive coupling between the first conductive film and the light blocking film in the structure in which the light blocking film is employed in the two-layer interconnection. This makes it possible to effectively prevent degradation in the image signal at the single-layer interconnection of the image signal line.
In the mode of the electrooptical apparatus according to the first aspect of the invention in which the part made of the light blocking film is covered with the part made of the second conductive film, in the two-layer interconnection, the part made of the light blocking film may have an interconnection width smaller than the part made of the second conducive film.
This technique ensures that the increase in the capacitive coupling between the first conductive film and the light blocking film is suppressed.
According to a second aspect of the present invention, to solve the above problems, there is provided an electrooptical apparatus including an electrooptical material disposed between a pair of substrates wherein, on one of the substrates, there are provided: a plurality of scanning lines; a plurality of data lines; thin-film transistors connected to the plurality of scanning lines, respectively, and also to the plurality of data lines, respectively; pixel electrodes connected to the respective thin-film transistors; an electrically-conductive light blocking film disposed such that at least the channel region of each thin-film transistor is covered with the light blocking film when viewed from the side of the one of substrates; a plurality of image signal lines that supply an image signal; and a sampling circuit that samples the image signals supplied via the plurality of image signal lines and supplies the resultant signals to the plurality of data lines, respectively; wherein at least a part of each of relay interconnections connecting the image signal lines to the sampling circuit is made of the light blocking film.
In the electrooptical apparatus according to the second aspect of the invention, because at least a part of each of relay interconnections connecting the image signal lines to the sampling circuit is made of the light blocking film, it is possible to obtain a lower resistance for the relay interconnections compared with the case where, of thin film layers forming the thin-film transistors, the data lines, and the scanning lines, the second conductive film having a lower conductivity than the first conductive film is selected as the material of the relay interconnections. If the light blocking film is formed of, for example, a refractory metal film having electrical conductivity, it is possible to greatly reduce the interconnection resistance of the relay interconnections. In this case, the light blocking film serves not only as a film that prevents the thin-film transistors from being exposed to light but also as a peripheral interconnection, and thus the construction and the production process can be simplified.
In this technique, because the image signals are input to the sampling circuit via the relay interconnections having low resistance, the driving frequency of the electrooptical apparatus can be increased, or the number of expanded phases, or the number of image signals which are input in parallel can be increased without causing voltage fluctuations, ghosts, or crosstalk due to capacitive coupling associated with the relay interconnections of, for example, image signal lines, which are problems in the conventional technique, thereby ensuring that a high-quality image is displayed.
In one mode of the electrooptical apparatus according to the second aspect of the invention, at least a part of sampling circuit driving signal lines that supply a sampling circuit driving signal to the sampling circuit is made of the light blocking film.
In this mode, because at least a part of sampling circuit driving signal lines is made of the light blocking film with electrical conductivity, it is possible to obtain a lower resistance for the sampling circuit driving signal lines compared with the case where, of thin film layers forming the thin-film transistors, the data lines, and the scanning lines, the second conductive film that has a lower conductivity than the first conductive film is selected as the material of the sampling circuit driving signal lines. Because the sampling circuit drive signals are input to the sampling circuit via sampling circuit driving signal lines having low resistance, it is possible to display a high-quality image.
To solve the problems described earlier, the invention provides a first method of producing an electrooptical apparatus including an electrooptical material disposed between a pair of substrates wherein, on one of the substrates, there are provided: a plurality of scanning lines; a plurality of data lines; thin-film transistors connected to the plurality of scanning lines, respectively, and also to the plurality of data lines, respectively; pixel electrodes connected to the respective thin-film transistors; an electrically-conductive light blocking film disposed such that at least the channel region of each thin-film transistor is covered with the light blocking film when viewed from the side of the one of substrates; a plurality of image signal lines that supply an image signal; and a sampling circuit that samples the image signals supplied via the plurality of image signal lines and supplies the resultant signals to the plurality of data lines, respectively; the method including the steps of: forming the light blocking film and first relay interconnections that connect the image signal lines to the sampling circuit using the same material; forming a first interlayer insulating film on the first relay interconnections and the light blocking film; forming the scanning lines on the first interlayer insulating film and also forming a second relay interconnection connected to the first relay interconnection via a contact hole formed in the first interlayer insulating film; forming a second interlayer insulating film on the scanning lines and the second relay interconnection; and forming the data lines connected to the thin-film transistors via contact holes formed in the second interlayer insulating film and also forming the image signal lines connected to the second relay interconnection.
In the first method of producing the electrooptical apparatus according to the invention, the light blocking film and the first relay interconnections that connect the image signal lines to the sampling circuit are formed using the same material. This allows simplification in the production process. Then the first interlayer insulating film is formed on the first relay interconnections and the light blocking film, and scanning lines are formed on this first interlayer insulating film. The second relay interconnection is then formed such that it is connected to the first relay interconnection via a contact hole formed in the first interlayer insulating film. The second interlayer insulating film is then formed on the scanning lines and the second relay interconnection. After that, the data lines connected to the thin-film transistors via contact holes formed in the second interlayer insulating film and also the image signal lines connected to the second relay interconnections are formed. Thus, in this technique, because the image signals are input to the sampling circuit via the relay interconnections that have low resistance, it is possible to produce an electrooptical apparatus capable of displaying a high-quality image, even if the driving frequency of the electrooptical apparatus is increased, or the number of expanded phases, or the number of image signals which are input in parallel is increased.
To solve the problems described earlier, the invention also provides a second method of producing an electrooptical apparatus including an electrooptical material disposed between a pair of substrates wherein, on one of the substrates, there are provided: a plurality of scanning lines; a plurality of data lines; thin-film transistors connected to the plurality of scanning lines, respectively, and also to the plurality of data lines, respectively; pixel electrodes connected to the respective thin-film transistors; an electrically-conductive light blocking film disposed such that at least the channel region of each thin-film transistor is covered with the light blocking film when viewed from the side of the one of substrates; a plurality of image signal lines that supply an image signal; and a sampling circuit that samples the image signals supplied via the plurality of image signal lines and supplies the resultant signals to the plurality of data lines, respectively; the method including the steps of: forming the light blocking film and first relay interconnections that connect the image signal lines to the sampling circuit using the same material; forming a first interlayer insulating film on the first relay interconnections and the light blocking film; successively forming a plurality of films into a multilayer structure on the first interlayer insulating film, the plurality of films including a semiconductor layer acting as a source and drain of each thin-film transistor, a gate insulating film, and a gate electrode; forming a second interlayer insulating film on the gate electrode; and forming the data lines connected to the thin-film transistors via contact holes formed in the second interlayer insulating film and also forming image signal lines connected to the first relay interconnections via contact holes formed in the first and second interlayer insulating films.
In the second method of producing the electrooptical apparatus according to the invention, the light blocking film and the first relay interconnections for connecting the image signal lines to the sampling circuit are formed using the same material. This allows simplification in the production process. After that, the first interlayer insulating film is formed on the first relay interconnections and the light blocking film. Furthermore, the semiconductor layer acting as a source and drain of each said thin-film transistor, the gate insulating film, and the gate electrode are successively formed into the multilayer structure on the first interlayer insulating film. The second interlayer insulating film is then formed on the gate electrode. Furthermore, the data lines connected to the thin-film transistors via contact holes formed in the second interlayer insulating film are formed. After that, the image signal lines connected to the first relay interconnection via contact holes formed in the first and second interlayer insulating films are formed. Thus, in this technique, because the image signals are input via the relay interconnections that have low resistance, it is possible to produce an electrooptical apparatus capable of displaying a high-quality image, even if the driving frequency of the electrooptical apparatus is increased, or the number of expanded phases, or the number of image signals which are input in parallel is increased.
These and other features and advantages of the present invention will become more apparent from the following detailed description referring to the following drawings.